The field of the invention is synthetic resins having pore forming and the present invention is particularly concerned with expandable styrene polymers suitable for the production of rapidly mold-ejected cellular bodies containing therein a reacted, uniformly distributed compound of high molecular weight forming a non continuous phase.
The state of the art of preparing fine particulate, expandable styrene polymers suitable for the production of cellular bodies which are rapidly ejected from molds may be ascertained by reference to U.S. Pat. Nos. 2,857,339; 2,857,340; 3,224,984; 3,468,820; 3,503,905; 3,503,908; 3,558,534; 3,972,843; and 4,243,717; British Pat. Nos. 1,083,040; 1,172,292; 1,297,105; and 1,106,143; West German Published Application No. 1,959,729; and Japanese Patent Document No. 71/21,453, the disclosures of which are incorporated herein by reference.
The preparation of the polyoctenamer starting material of the present invention is disclosed in CHEMIKER-ZEITUNG, Vol. 99 (1975), pp. 397-413, the disclosure of which is incorporated herein by reference.
It is known to manufacture molded foam bodies by expanding fine-particulate styrene polymers in molds. In this process, fine particulate, expandable styrene polymers first are subjected by means of steam or hot gases to a prefoaming process. The prefoamed particles are first stored and then are final foamed further in perforated molds with superheated steam, and sintered. Following this final foaming to completion, the molded body must remain some additional time in the mold until it has cooled sufficiently to be removed without warping its shape. This dwell time in the mold is designated as the minimum mold dwell time or the cooling time and represents a down time which one tries to minimize to optimize mold use.
Especially those expandable styrene polymers which are made flame-retardant by means of organic halogen compounds more readily form products with irregular cell structures. Foam blocks made of such flame retardant particles following mold ejection are more susceptible to having their sides collapse (block shrinkage) and are rather more weakly welded together inside the block.
It is desirable, when prefoaming the beads, that part of the prefoamed beads be prevented from shrinking. As a result, the desirable low densities of the molded bodies are not achieved. Furthermore, a high loss in expanding agent is related to the shrinkage, whereby again the above-mentioned drawbacks of block shrinkage and inadequate fusion inside the molded body are incurred. Lastly, an uneven surface of the molded body is the result.
A number of processes have become known which make it possible to shorten the cooling times and hence to obtain ejected molded bodies more rapidly, for instance by coating the expandable or prefoamed particles with paraffin oil as disclosed in British Pat. No. 1,083,040, and West German Published Application No. 1,959,729, or with oil soluble emulsifiers as disclosed in U.S. Pat. No. 3,503,908. Further, it is taught that rapidly ejected cellular bodies can be obtained provided the expandable particles contain slight amounts of water in finely distributed form during manufacture, as disclosed in British Pat. No. 1,106,143, or when the manufacture of the expandable particles is carried out by polymerizing in the presence of slight amounts of certain bromine compounds as disclosed in U.S. Pat. No. 3,503,905 and British Pat. No. 1,172,292. In a series of prior art processes the polymerization is also carried out in the presence of slight amounts of polystyrene incompatible polymers as disclosed in British Pat. No. 1,297,105, U.S. Pat. Nos. 2,857,339; 2,857,340; 3,224,984; 3,558,534; and 3,468,820; and Japanese patent application No. 71/21,453, a low cooling time having been observed in part, but in part also the additives exerting practically no effect on the cooling time. The following are listed as incompatible polymers: polyethylene, atactic polypropylene, polyisobutylene, polyvinylidene chloride, copolymers of ethylene and vinylacetate or of styrene, acrylonitrile and N-vinylcarbazole, or condensation products of phthalic acid and hexane triol, further such elastomers as butadiene-styrene copolymers, polybutadiene, and polyisoprene are incompatible polymers also.
U.S. Pat. No. 3,972,843 discloses the use of butene-(1) polymers or copolymers as additives to reduce the minimum mold dwell time. Fischer-Tropsch waxes are disclosed in U.S. Pat. No. 3,972,843 (control tests 1g and h) and in U.S. Pat. No. 4,243,717.